The present invention relates to conveyor roll bearings, and more particularly to light-duty conveyor roll bearings.
A wide variety of conveyor roll bearings has been developed to rotatably support a conveyor roll in a conveyor system. Typically, the conveyor roll is hollow and one bearing is press-fitted into each of the opposite ends of the roll to rotatably mount the roll on a frame. Each bearing includes an inner race assembly mounted on a support shaft and an outer race assembly rotatably supporting the conveyor roll. A row of balls is positioned between the two race members to rotatably support the outer race member on the inner race member.
In particular, a variety of light-duty conveyor roll bearings has been developed to provide requisite load-bearing characteristics at a reasonable cost. These light-duty bearings are utilized in a variety of environments including electronic assembly, cosmetic manufacture, breweries, and retail warehouses. One such bearing includes a stamped, cup-shaped, outer bearing member; an inner race member; and a ball row positioned within the raceway defined by the inner and outer race members. The cup-shaped outer race member facilitates assembly because the inner race with the balls positioned thereabout may be simply dropped into the outer race. The open side of the cup-shaped outer race is then closed by a hardened thrust washer held in position by a separate retainer crimped about the body of the outer race. Thrust washers are required in these nonprecision bearings because the noncritical tolerances permit relative axial movement of the bearing elements. Although this bearing is adequate in many applications, it is not without its drawbacks.
First, one or both of the sides of the ball raceway are open between the inner and outer race members. Therefore, the bearing is subject to contamination and lubricant loss. Second, the cup-shaped outer race must be closed at its open end by a relatively expensive, two-piece assembly including a hardened thrust washer and a softer retaining piece securing the thrust washer in position. Third, conveyor roll bearings are typically noisy because of the metal-to-metal contact between the bearing and the support shaft. Although some artisans have attempted to alleviate noise problems by including a polymeric, vibration-absorbing hub between the bearing and the support shaft, this attempted solution insulates the conveyor rolls and causes them to build up static charges as a result of conveyor operation. These charges are particularly undesirable in electronics applications.